1. Field of the Invention
The present invention relates to apparatus and methods for transferring data between a source and a plurality of receiving data processing devices. More particularly, the present invention relates to data transfer along a local area network between a plurality of data processing and peripheral devices.
2. Art Background
In the computing industry, it is quite common to transfer data and commands between a plurality of data processing devices, such as for example, computers, printers, memories and the like. The interconnection of computers and other peripheral devices principally developed in the early 1970's with the advent of computer networking systems, which permitted the distribution of access to computing resources beyond the immediate proximity of a main frame computer.
Networks, such as the ARPA Network, were developed to provide access by various users to large time-sharing systems and the transfer of data between such systems. In the case of geographically local networks, so called "local area networks" (LANs) were developed to connect together a collection of computers, terminals and peripherals located, typically in the same building or adjacent buildings, and permitted each of these devices to communicate among themselves or with devices attached to other networks. Local area networks permit the implementation of distributed computing. In other words, some of the devices coupled to the local area network may be dedicated to perform specific functions, such as file storage, data base management, terminal handling, and so on. By having different machines perform different tasks, distributed computing can make the implementation of the system simpler and more efficient.
Local area networks differ from their long-haul cousins in a number of respects. A key difference is that the designers of long-haul networks, such as the ARPA network, are often forced by economic or legal reasons to use the public telephone network, regardless of its technical suitability. In contrast, most local area networks utilize their own high-bandwidth cable to permit datagram service between the various devices coupled to the LAN. The most common transmission media for carrier sense local area networks are co-axial cable, twisted pair and fiber optics. A variety of cable topologies are possible, such as linear, spine, tree, ring and segmented. In addition, local area networks do not suffer from the long propagation delays which are inherent with other large networks, thus allowing the channel utilization to be pushed significantly above the capabilities of large scale networks.
Although local area networks hold the promise of distributed processing and communication between data processing devices, a number of factors have prevented wider use and acceptance of local area networks, such as ETHERNET (U.S. Pat. No. 4,063,220). For example, despite efforts to lower costs using VLSI technology, a typical LAN node may represent a significant percentage of the total cost of a personal computer. Accordingly, in the personal computer market local area networks have been prohibitively expensive to implement. In addition, most local area networks utilize complex cabling techniques and require a system administrator who is trained in the installation, updating and maintainence of the LAN system. Moreover, many local area networks utilize relatively complex protocols to permit the various devices coupled to the LAN to communicate under various conditions.
As will be decribed, the present invention provides a local area network for communication and resource sharing among various computers, servers, disks, printers, modems and other data processing devices. The present invention supports a wide variety of local area network services, and permits communication to larger networks through the use of bridging devices. The present invention provides an economical, reliable, and mechanically simple local area network heretofore unknown in the prior art.